Varroa mite calculator for an alcohol wash or sugar roll
Count the mites from your wash or sugar roll, enter how many bees were in the sample, and pick the season. The result is mites per 100 adult bees, next to the threshold the source you pick uses for that time of year.
How the number is worked out
Mites per 100 bees is the mites counted, divided by the bees in the sample, times 100. Beekeeping guides write it as a percentage, so "3 percent" means 3 mites per 100 adult bees. The worked example in the Honey Bee Health Coalition's Tools for Varroa Management guide is 12 mites in 300 bees: 12 ÷ 300 × 100 = 4 percent.
The count only covers mites on adult bees. Mites inside capped brood cells don't show up, so the guide calls the result an estimate, and a zero doesn't mean the colony has no mites.
How many bees are in half a cup
Sources differ. The Honey Bee Health Coalition guide (9th edition, June 2026) says 300 bees are about half a cup of lightly packed bees, and suggests counting the bees in each sample for a more accurate result. Mississippi State Extension's alcohol wash guide (Publication 4049) puts half a cup of nurse bees at about 400.
The gap matters close to a threshold. The line under the result shows your mite count against both sample sizes. The Honey Bee Health Coalition guide also notes that a sample of fewer than 300 bees isn't accurate.
The thresholds this page uses
Mites per 100 adult bees. At or above the number counts as above the threshold.
| Source | Phase or month | Threshold |
|---|---|---|
| Honey Bee Health Coalition | Dormant | 1 |
| Honey Bee Health Coalition | Population Increase | 1 |
| Honey Bee Health Coalition | Peak Population | 2 |
| Honey Bee Health Coalition | Population Decrease | 2 |
| Mississippi State Extension | February | 1 |
| Mississippi State Extension | May to October | 3 |
- Honey Bee Health Coalition, Tools for Varroa Management, 9th edition, Table 1. The phases follow the colony's own yearly cycle, which shifts with region: Population Increase is the spring buildup, Peak Population is when the colony is largest and supers are often on, Population Decrease comes after the honey harvest while the colony raises its winter bees, and Dormant is the clustered winter colony (a footnote to Table 1 says to sample a dormant colony just before it clusters). The guide calls these conservative estimates and says thresholds vary by region.
- Mississippi State Extension, Sampling for Varroa Mites Using Alcohol Wash, Publication 4049. It gives 1 per 100 for a February sample and 3 per 100 for the rest of the season, May through October, in a guide written for Mississippi beekeepers. It gives no number for March, April or November to January, so this page doesn't either.
Alcohol wash or sugar roll
Both start with about half a cup of adult bees shaken from one to three brood-nest frames, with the queen set aside first. An alcohol or low-sudsing soap wash kills the sampled bees. In a powdered sugar shake the bees go back to the colony afterwards, though the guide notes they may or may not survive. The Honey Bee Health Coalition guide calls the wash the more reliable method and applies the same Table 1 thresholds to both.
When to sample
The Honey Bee Health Coalition guide suggests sampling monthly from the start of Population Increase, or at least four times from Peak Population into the decline, and more often in the fall so the colony goes into winter with a low count. It also says to sample again after any treatment to check it worked. Mississippi State Extension asks beekeepers in Mississippi to sample at least in early February and early July.
If the count is above the threshold
This page only does the math, and it doesn't recommend treatments. The Honey Bee Health Coalition's Tools for Varroa Management guide lists the control options for each colony phase, with the conditions each one needs. Your state apiarist, extension office or local bee club can tell you what works in your area. Follow the label of whatever you use.
Other calculators
- Winter honey stores calculator: estimated pounds of honey from your frames, against a winter target.
- Sugar syrup calculator: sugar and water for 1:1 or 2:1 syrup.